The embodiments described herein relate generally to medical devices and pharmaceutical compositions, and more particularly to a medicament delivery device for delivery of drugs to infants and children.
Exposure to certain substances, such as, for example, peanuts, shellfish, bee venom, certain drugs, toxins, and the like, can cause allergic reactions in some individuals. Such allergic reactions can, at times, lead to anaphylactic shock, which can cause a sharp drop in blood pressure, hives, and/or severe airway constriction. Accordingly, responding rapidly to mitigate the effects from such exposures can prevent injury and/or death. For example, in certain situations, an injection of epinephrine (i.e., adrenaline) can provide substantial and/or complete relief from the allergic reaction. In other situations, for example, an injection of an antidote to a toxin can greatly reduce and/or eliminate the harm potentially caused by the exposure. Because emergency medical facilities may not be available when an individual is suffering from an allergic reaction, some individuals carry a medicament delivery device, such as, for example, an auto-injector, to rapidly self-administer (or to have a care giver administer) a medicament in response to an allergic reaction. Moreover, even within a medical facility (e.g., a hospital, doctor's office, clinic, or the like) automatic delivery devices can be advantageous. Specifically, such devices include a predetermined dosage that is appropriate for the patient, and provide a method for repeatably and reliably delivering the dose. Accordingly, there are many known devices for automatically delivering epinephrine.
Some known devices for automatically delivering epinephrine, such as the Epipen®, include a needle that is automatically inserted into the body and through which the dose is injected into the patient. Such known devices target intramuscular delivery of the epinephrine (e.g., delivery into the thigh muscle). In fact, some studies have shown that subcutaneous delivery of epinephrine can reduce the efficacy of the dose. Moreover, some studies have shown that intravenous delivery of epinephrine can not only reduce the efficacy, but also can result in cardiovascular complications (e.g., a rapid rise in blood pressure and increased heart rate). In addition to concerns with subcutaneous and intravenous delivery, intraosseous delivery of epinephrine is also undesirable.
Known auto-injectors include devices tailored for both adult use and pediatric use. In particular, known adult-use auto-injectors typically include a dose of 0.3 mg epinephrine, and are used for patients weighing greater than 30 kg. The exposed needle length for such known adult-use auto-injectors ranges from about 16 mm to greater than 20 mm. Known pediatric auto-injectors typically include a dose of 0.15 mg epinephrine, and are used for patients weighing between about 15 kg and 30 kg. Such known pediatric-use auto-injectors typically have a shorter exposed needle length to accommodate the smaller size of the patient—often between 12.7 mm and 16 mm. Currently, however, there are no known devices for automatically injecting epinephrine into infants and small children weighing less than 15 kg.
Because there are no products available for use with this patient population, in certain instances a pediatric-use auto-injector may be used with a child weighing less than 15 kg. Such use, however, can present complications due to the possibility of overdosing the patient. Further complicating this concern is the fact that the dose accuracy for a device intended to deliver 0.3 mL (or 0.15 mL for a pediatric version) may not be adequate for a patient weighing less than 15 kg. More particularly, the volumetric tolerance for a device configured to deliver 0.3 mL with an accuracy of ±15 percent is ±0.045 ml. This volumetric tolerance may not be sufficient for patient weighing less than 15 kg.
Another concern with using an auto-injector intended for patients weighing more than 15 kg is the possibility that the dose will be delivered to an improper location within the body. In particular, because the distance between the skin and the muscle layer (referred to herein as the skin-to-muscle distance) and between the skin and the bone (e.g., the femur, referred to herein as the skin-to-bone distance) is different for patients weighing less than 15 kg than it is for larger patients, the use of a device intended for larger patients may result in intraosseous delivery in an unacceptable number of patients. If the exposed needle length is made too short, however, then undesirable subcutaneous delivery may also occur in an unacceptable number of patients.
Thus, a need exists for improved methods and devices for delivering drugs, and in particular, epinephrine, to infants and children weighing less than 15 kg. Additionally, a need exists for an epinephrine auto-injector having improved accuracy.